1. Technical Field
The present invention relates to a mold unit which is employed in molding a resin molded product, and also relates to a module for electrical connection including a housing which is obtained by resin molding employing the mold unit and used for assembling various components for electrical connection, and snap fits which are integrally formed on the housing for assembling the components.
2. Background Art
As a representative example of the module for electrical connection which is constructed by assembling various components for electrical connection such as bus bars, terminals, and circuit boards, there is an electrical junction box which is used in a wiring system in a vehicle, for example.
A representative example of structure of the electrical junction box is shown in FIG. 5. An electrical junction box 1 in this example includes a housing 2 which is obtained by resin molding. The housing 2 has a component assembling part 3 to which electrically conductive elements such as bus bars 4 (bus bars 4a, 4b, and so on) and terminals 5 are assembled by insert molding. portions of the bus bars 4a, 4b are respectively exposed from windows 6 (windows 6a, 6b, and so on) provided in the component assembling part 3. Moreover, a fit-in mounting part 7 is provided in the component assembling part 3, and a bus bar 8 to be fitted later is assembled to this fit-in mounting part 7 by fit-in mounting, as an electrically conductive element to be fitted later by non-inserting. Further, snap fits 11 are integrally formed at four positions in the component assembling part 3 so that the components such as circuit boards, which are not shown, can be assembled in a snap-fitting structure, by means of these snap fits 11 at the four positions.
As shown in an enlarged view in FIGS. 6A and 6B, each of the snap fit 11 has a base part 12 in a columnar shape which is integrally formed in the component assembling part 3, and a pair of snap pieces 13, 13 which are extended from the base part 12 axially symmetrically in a manner of interposing a deforming gap 14 between them. The snap pieces 13, 13 respectively have leg portions 15 and locking head portions 16, and are so constructed that taper faces 17 formed on the locking head portions 16 are pressure-contacted to an assembling hole which is formed in the mating component to be assembled (not shown), whereby the snap pieces 13, 13 are deformed into a state where the deforming gap 14 is narrowed.
In integrally molding the snap fits 11 in the component assembling part 3 at a time of molding the housing 2, it is unavoidable that an error to a certain extent may occur in the positions of the snap fits 11, due to molding conditions, and shrinkage or deformation of the resin at a time of molding, depending on a type of the resin to be used. By the way, in case of the electrical junction box, high accuracy is required in assembling the components, and accordingly, high accuracy is also required as for the positions of the snap fits 11. Therefore, it is necessary to modify a mold unit (hereinafter, appropriately referred to as “the mold”) according to the positional error of the snap fits in a molded product which has been produced as a prototype. However, there is a problem that modification of the mold is extremely difficult, in case where the housing 2 of the electrical junction box 1 is produced by resin molding.
In FIGS. 7 and 8, structure of a mold in a region where the snap fit is molded is shown. FIG. 7 shows relation between the mold and the snap fit 11 at a time of molding, and FIG. 8 shows relation between the mold and the snap fit 11 after molded. The mold in the region where the snap fit is molded is so constructed that a snap fit die 22 for molding the snap fit 11 is incorporated in a fixed core 21. From such structure of the mold, it is unavoidable that the region for molding the snap fit is positioned on a dividing surface 23 of the mold, which is a factor responsible for making modification of the mold extremely difficult.
As an art for assembling the circuit boards in the snap-fitting structure, there has been known, for example, the art disclosed in JP-A-2007-59753.
As described above, in case where the snap fits for assembling the components are formed, by integral molding, in the housing of the module for electrical connection such as the electrical junction box which is formed by resin molding, there has been such a problem that modification of the mold for eliminating the positional error of the snap fit is extremely difficult, because the region where the snap fit is molded is positioned on the dividing surface of the mold. Therefore, it has been required to solve this problem.